Brakes continually need re-bleeding / reservoir needs topping up

[Paul Smith]

My Jubilee has spent a lot of the last couple of years not being used but until recently I have not had any real problems, but now I have a problem with the brakes.

I found I had no brakes at all, I noticed that the fluid level was a bit low so topped it up and did a full bleed on the brakes. I got a decent pedal after a couple of attempts. Now after being in the body shop for some repairs the brakes have gone again. The reservoir fluid level is again low but there is no apparent signs of a leak. Nothing on the floor and certainly no leaks from the wheel cylinders.

Can anyone advise were next to look.

Thanks,

Paul

[Bumpa]

It's not unheard of for the fluid to be collecting in the brake servo, assuming you have the remote servo mounted on the passenger side of the car. A few owners have suffered sudden alarming loss of brakes while driving when all the brake fluid has gone into the servo. It's what I would check if I were you.

[Paul Smith]

Thanks I will check that when I get to the car.

Paul

[Michael Barclay]

Hello Paul
I would agree with Mike. I experienced the same problem a couple of years ago and suffered complete brake failure. Couldn't find any leaks but when I removed the Servo, the main vacuum chamber was full of fluid. A tell-tale sign is white smoke from the exhaust as brake fluid is sucked into the engine via the inlet manifold vacuum line. You can buy a repair kit and its a fairly easy job to replace the seals.
Best regards
Mike Barclay

[Bumpa]

Or simply remove the servo and connect up the pipework without one. In my opinion the standard servo makes very little difference to the brakes anyway. Plus you will have a firmer pedal. After all, the first nine years of MGBs had no servo, and the brakes were identical to the ones on the servoed cars.

[Dave Wheatley]

Or simply remove the servo and connect up the pipework without one. In my opinion the standard servo makes very little difference to the brakes anyway. Plus you will have a firmer pedal. After all, the first nine years of MGBs had no servo, and the brakes were identical to the ones on the servoed cars.

I have a feeling that the master cylinder on the servo cars has a different bore size, and that the brake pads have different friction characteristics. I do know that on some other makes of car, removing the servo makes the braking non existant. 1960s Jaguars for example.

[Bumpa]

According to the official parts book and Clausager's "Original MGB", all single circuit brakes on the MGB use the same master cylinder. There was a change to the type of seals used but the bore remained the same. There is a good article on the servo on Paul Hunt's excellent site http://mgb-stuff.org.uk/braketext.htm#servo. I am stealing this paragraph from that article as it mirrors my own experience.

"Originally the remote servo was an option, which means that braking performance without the servo must be adequate at least, and in fact this servo only gives light assistance. I've driven V8s (on which it was standard) with and without this servo operational and even though the first time I drove one without and was looking for the difference, I was amazed at how little it was, and after a couple of test prods I didn't notice it at all in normal driving. I believe the later integral servo does give more assistance, and the master cylinder diameter was reduced to give less pedal travel for the same overall retardation. This means that if the integral servo is not functioning the effects are much greater and significantly higher pedal pressures will be required for 'normal' levels of retardation. "

[Paul Hollingworth]

I don't agree, having driven B's with and without servos I consider they are a welcome addition. The brake feel with a servo is very good, it just requires less effort. I probably have a strong enough right leg to be able to lock all four without one but why make it harder than it needs to be. Just got to address the heavy steering now and perhaps the wife will drive me back from the pub. I too had my engine ingesting brake fluid through the servo so I replaced it. They are a b*gger to bleed.

[Bumpa]

Well I would agree about the steering and that's why my V8 has power steering. But my 1971 roadster, which I drove to work every day for 12 years has no servo and the brakes were absolutely fine and not heavy at all. Far better than on my 1977 Dolomite which does have a servo! I'm currently rebuilding the roadster and I won't be fitting a servo.

My V8GT is a bit special and has much bigger front brakes plus rear discs, so I converted it to dual circuit braking with the in-line mechanical servo. That doesn't need bleeding and is not likely to suck up my fluid either!